The ultimate aim of this project is to attempt to perfect a vaccine containing purified (enterobacterial) common antigenic determinant(s) which would give rise to antibodies for protecting against a variety of infections due to enterobacteriacea. We are studying the antigenic relationships (if any) between enterobacterial CA (ECA) and Re antigens. We have already provided evidence for the anatomical locus of ECA by isolating the cell envelope, membrane vesicles, soluble cytoplasmic components and finally pure outer and inner membranes from E. coli 014 and S. typhimurium and have also studied the serologic reactivity of pure outer and inner membranes from these organisms with a variety of CA containing antisera. Presently we are investigating the antigenic character of pure outer and inner membranes from Re mutants in serologic tests. Our specific research goal for this coming year is to purify the smallest component of enterobacterial common antigen(s) which retains immunogenicity and hopefully gives rise to protective antibodies as contrasted to a purified component which may be only serologically reactive. If we are able to fulfill this goal, chemical characterization of the active components should then be possible.